Epitaxial growth of indium oxyfluoride thin films by reactive pulsed laser deposition: Structural change induced by fluorine insertion into vacancy sites in bixbyite structure

InO_xF_y thin films were epitaxially grown on Y-stabilized ZrO₂ (111) substrates by reactive pulsed laser deposition. By changing the substrate temperature (T_S), we were able to control the fluorine content of the film. Phase-pure epitaxial thin films with bixbyite-like ordering in the anion-site occupancy were obtained at high T_S (≥ 240 °C), where fluorine was inserted into the vacancy sites in the bixbyite lattice up to y / (x + y) ∼ 0.3. By decreasing T_S, y / (x + y) increased and the bixbyite-like ordering disappeared; simultaneously, fluorine-rich and fluorine-poor subphases emerged. The films grown at T_S ≤ 150 °C were amorphous and exhibited higher optical absorbance and electrical resistivity than the epitaxial films. - Highlights: • InO_xF_y epitaxial thin films with high fluorine concentration were grown on Y:ZrO₂. • Anion composition and structural, optical and transport properties were studied. • Fluorine is topotactically inserted into the oxygen vacancy sites in bixbyite cell. • Bixbyite-like ordering of the anion site occupancy was conserved in y / (x + y) ≤ ∼ 0.3